BH stands for Begleithundprüfung, it's basically a temperament test. It's a test a dog has to pass before moving on to Schutzhund/IPO to be titled. AD stands for AusdauerprÜfung and is an endurance test which'll indicate whether or not a dog is able to physically exert itself to a certain degree without showing extreme signs of fatigue. If anything, most fails are due to injuries with the DH, though it's pretty easy to pass.
The DDR is no longer really around, the DDR bloodlines are but it's far from what it was a long time ago. It's a line of working dogs, just like other working lines like Czech and West German working lines.